Sometimes, however, it is not possible to compute the best k results. For example, let’s assume that we want to book a train between Milan and Rome and we are looking for a cheap ticket on a high-speed train. As we might expect, high-speed trains tend to be more expensive than normal ones, so we cannot properly classify the tickets as cheap. The purpose of skyline queries [1]} is to solve this problem by displaying the most interesting results to the end-user. Skylines are based on the concept of dominance, meaning that a point dominates another point only if it is as good or better in all the dimensions and better in at least one dimension. Points that aren’t dominated by other points make up the skyline.
